Synthesis of nano structural WC-Co powders from water soluble precursors: Effects of tungsten source and synthesis atmosphere on chemical and phase structure evolutions

Thermal sprayed cemented carbides such as WC-Co(Cr) and Cr3C2-NiCr coatings are widely used in wear protection purposes. Submicron and multimodal carbides in cermets showed promising results in hardness and wear performance. Presented study is a part of the research aiming to create a new novel powder manufacturing route for homogenous nano WC + Co matrix powder for thermal spraying. Goal of this study was to compare the effects of raw materials (tungsten source) and synthesis atmospheres on synthesis steps and on chemical and phase structures of the final products. Powders were manufactured via spray drying method from water based solution with raw materials ammonium para tungstate (APT) or ammonium meta tungstate (AMT) as a tungsten source, glycine as a carbon source and cobalt acetate as a cobolt source. Dried products were heat treated in Ar and Ar-4H2 atmospheres at different temperatures. The thermal decomposition was studied by using Thermogravimetry (TGA) and evolved gas analysis with mass spectrometer. The morphology and particle size were analysed with scanning electron microscopy (SEM) and an X-ray diffractometer (XRD) was used for phase structure analysis. Results suggest that AMT is a better raw material as a tungsten source for this method. Heat treatment atmosphere have effects on the chemical and phase structure for raw materials but not for the final product.